Charge produced at the instant nanoparticles form upon rubbing of ash particle surfaces may solve the long-standing mystery of how lightning in volcanoes is electrified.
Background
The lightning observed in the plume of the Iceland volcano has renewed interest not only in how the volcano is electrified, but also how ice in the updraft of a thunderstorm produces lightning.
The electrification of volcanoes is generally thought caused by the rubbing of solid ash particles while that in thunderstorms is by the rubbing of ice particles. But the mechanism by which rubbing of particles produces the electrification has remained a mystery. See http://www.livescience.com/environment/volcano-lightning-Eyjafjallajokull-100420.html
Common belief is that rubbing removes electrons from particle surfaces, but this is unlikely because the electron is more tightly bound to the atom than the atoms are bound to each other, and therefore rubbing tends to only produce tiny clusters of neutral atoms called nanoparticles (NPs). Indeed, electrons are unlikely to be removed from a material by any form of mechanical energy. By the photoelectric effect, Einstein over a century ago showed only electromagnetic (EM) radiation may remove electrons from a material.
Hypothesis
Observation based on the foregoing allow the hypothesis that NPs comprising clusters of otherwise neutral atoms upon forming by rubbing solid surfaces somehow produce the EM radiation that by the photoelectric effect charges the NP by removing electrons.
Lightning by NPs in Thunderstorms
In the updraft of the thunderstorm, moisture is carried upward at high velocity and freezes at about 10,000 m. Submicron NPs may be formed directly from the moisture, but generally millimeter sized ice particles are produced. With the ice particles moving upward, other ice particles already having reached maximal height are falling downward to the earth under gravity. NPs generally form by the rubbing of particle surfaces in the collisions between upward and downward moving ice particles.
Of importance is the size differences between macroscopic particles and NPs. QM allows atoms in the macroscopic ice particles to have the thermal kT energy necessary absorb EM energy. Here QM stands for quantum mechanics, k for Boltzmann’s constant, and T for absolute. Classically, the atom in NPs is allowed to store the same amount of thermal energy as in macroscopic particles. But QM limits the amount of thermal energy stored by the atom depending on the particle size and temperature. At ambient and freezing temperatures, most of the thermal energy of the atom is stored at wavelengths greater than about 50 microns, but rapidly vanishes for NPs having wavelengths of a few microns. Therefore, at the instant the NPs form, the atoms have thermal energy in excess of that allowed by QM. If the NPs could increase in temperature, the excess thermal energy would be conserved. But QM also requires the specific heat of the atoms in NPs to vanish, and therefore the excess thermal energy cannot be conserved by an increase in temperature.
Conservation may only proceed by the QED induced up-conversion of the excess thermal energy in the FIR to the EM confinement frequency of the NP. Since the submicron size of the NP confines the FIR energy to EM frequencies in the UV and beyond, the NP spontaneously charge positive and emit electrons by the photoelectric effect. With the earth surface charged positive prior to the thunderstorm, the electrons attach to the downward falling ice particles and tend to charge the earth negative. Accumulation of charge from NPs during the storm therefore produces a large potential difference between the thundercloud and the earth that upon electrical breakdown creates cloud-to-ground lightning. However, the potential difference may occur within the thundercloud itself as commonly observed in cloud-to-cloud lightning.
However, only submicron NPs produce the ionizing radiation at UV or higher levels necessary to produce charge that electrifies the thunderstorm. Micron or larger sized ice articles that form on rubbing lack the EM confinement of thermal energy and only produce non-ionizing IR or FIR radiation.
Volcano Lightning by NPs
The charging process in volcanic lightning is similar to that in thunderstorms except that the NPs are produced by the rubbing of macroscopic particles of ash instead of ice. The ash particles are ejected from the volcano at high velocity only to collide and rub with those particles falling back to the volcano. Again, charge separation occurs as the positive charged NPs tend to move upward leaving the free electrons to attach to the downward falling particles.
Unlike thunderstorms, the ash need not move to high altitude to form solid particles, and therefore volcanic lightning is more efficient than that in thunderstorms, and therefore potential differences can reach breakdown over shorter separation distances. As shown in the thumbnail, volcano lightning is observed by electrical breakdown within the ash plume itself as in cloud-to-cloud lightning of thunderstorms.
Conclusions
The mysterious source of charge in thundercloud and volcano lightning finds commonality in the hypothesis that electrification in all natural processes is unified by rubbing NPs off solid surfaces. Other natural world mysteries possibly solved by NPs include Gecko walking on ceilings, X-rays from pulling Scotch tape from the roll, flow electrification in gasoline fires, ball lightning and St. Elmo’s fire, enhanced chemical reactions in tribochemistry. See “Unified Theory of Electrification in Natural Processes,” and other papers in http://www.nanoqed.org/ , 2009-10